Obsessive-Compulsive Disorder (OCD) is a prevalent and often chronic disorder that is currently treated with pharmacological and psychological approaches. Exposure combined with response prevention (ERP) is presently considered the psychological treatment of choice. However, many patients refuse, drop out of or are unresponsive to pharmacotherapy or ERP. Many patients never engage in treatment or experience significant impairment even after treatment. Further, ERP may be less acceptable to therapists and to managed care settings. Thus, additional interventions for the treatment of OCD that improve outcome are needed. Recent studies suggest that cognitive treatment (CT) for OCD is at least as effective as exposure and response prevention. Moreover, cognitive approaches may be less stressful and have lower refusal rates than intensive forms of exposure or pharmacotherapy. CT also appears to help patients with symptoms that do not benefit from standard treatment. Finally, CT may be more acceptable to therapists and health care settings. This proposal seeks funds to develop, systemize and pilot test a cognitive treatment for patients suffering from OCD based mainly on Beck's methods. This treatment is derived from a theoretical model of cognitive aspects and effects on OCD symptoms and from empirical evidence regarding interpretation of intrusions and beliefs found in patients with OCD. We propose to fully develop a treatment manual, and accompanying therapist adherence and competency measures. After the treatment development phase, we will apply cognitive therapy of three different durations to OCD patients to determine which format is clinically most useful. In the final phase, we will collect pilot data on the best version of the therapy in comparison to a wait-list control. We will investigate treatment effects on different cognitive domains, specific OCD symptoms, mood state and functioning. The effect size of cognitive therapy for a primary outcome variable, the Yale-Brown Obsessive Compulsive Scale and response rate of treated subjects will be determined, preparatory to a larger scale randomized controlled trial, if this is indicated. Using a combined sample of 30 patients we will study the influence of a small number of possible predictors of posttest outcome.